I have a house built in 1920 or so; 1000 sq feet. 2/3 of the house has a basement with concrete floors. The front third of the house has foundation walls that are only 5 feet; the walls sit on dirt that extends at a 45 degree angle to the dirt floor (which is level with the rest of the basement). Over the years, this front section has sagged a little and the foundation has cracked. I am also getting water leaking through the dirt. I would like to pour a concrete floor in this section over the dirt.
Big question: how to hold up the 5 foot foundation walls? Should I dig underneath the walls and then pour concrete in sections? What other alternatives are there? I am looking to get this done soon. I have spoken to a concrete guy who wants dig away the 45 degree dirt and pour a footing 18in inside the 5 foot wall; then pour a 3 foot inner wall. I am unsure how this would help shore up the additional foundation. Any input??

Welcome 2Dogger:
We don't know how many years this situation has existed but it hasn't fell in yet. That says a whole lot.
I would consider a footer at the bottom of the 45* with a keyway in it and #4reinforcing rods sticking out every 2' and leaning twoard the angle. Drill holes in the foundation above at 2' intervals corresponding to the lower rods. Stick rods into the upper holes and tie them to the lower rods. Now, place a reinforcing mat of rods on 1' each way. Place 6" of concrete on the 45* slope and pour a floor below. This gives a 'knee wall' to keep the foundation from slipping into the basement and will help to hold it up, vertically at the same time.

Thanks Glenn. I spoke to my contractor and we will be doing just that. I am in the process of digging right now (my back is a bit sore throwing all the dirt out the window). We should be pouring by the end of the week.